1. Field of the Invention
The present invention relates to a recording apparatus for discharging recording liquid such as ink from a discharge port to form a liquid droplet thereby executing a recording operation, and an ink jet recording head to be used therein. The ink jet recording head of the present invention is applicable not only to a general printing apparatus but also to an apparatus such as a copying apparatus, a facsimile apparatus having a communication system or a word processor having a printing unit, and also to an industrial recording apparatus combined in complex manner with various processing apparatus.
2. Related Background Art
The ink jet recording apparatus is a recording apparatus of so-called non-impact type capable of high-speed recording as well as recording on various recording media and is featured by scarce noise generation in recording. Because of these facts, the ink jet recording apparatus is widely employed in the recording mechanism in the printer, copying apparatus, facsimile, word processor etc.
As the representative ink discharging methods in the recording head mounted in such ink jet recording apparatus, there are already known a method of employing an electromechanical converting member such as a piezo element, a method of generating heat by irradiation of an electromagnetic wave such as laser light and discharging an ink droplet by the action of such heat, and a method of heating ink with an electrothermal converting element including a heat generating resistance member and discharging an ink droplet by the action of film boiling. In an ink jet recording head utilizing an electrothermal converting element, such electrothermal converting element is provided in a recording liquid chamber and is given an electric pulse constituting a recording signal to generate heat thereby providing ink with thermal energy and inducing a phase change (boiling) in the recording liquid, thus generating a bubble in the recording liquid, and the pressure of thus generated bubble is utilized to discharge a small ink droplet from a small discharge port to form a record on a recording medium, and there are generally provided an ink jet recording nozzle for discharging ink droplet and a supply system for supplying the nozzle with the ink.
In such ink jet recording head, the interior of the recording liquid chamber is exposed to a high temperature by the heat generation of the electrothermal converting element. It is therefore desirable to select such ink that is not denatured by such high temperature and to cover various elements on the substrate with a protective film in order that the elements of the electrical circuit etc. are not damaged by the heat. Also since the metal surface may be eroded by impact at the extinction of the bubble generated by heating, there is preferably provided a protective film (anticavitation film) for preventing such erosion.
In the conventional ink jet recording head, recording elements and electrical circuit elements are formed on a substrate, then a protective film for providing heat resistance is formed thereon, and then an anticavitation film is formed thereon over the entire surface. In such state, members for forming a discharge port are formed thereon. The discharge port forming members include flow path walls for defining a flow path corresponding to each recording element and a discharge port through which the flow path communicates with the exterior. The above-described configuration attains an effect of protecting the recording elements and the electrical circuit elements, but there are encountered other drawbacks.
Firstly, a tantalum (Ta) film generally employed as the anticavitation film adheres only poorly to the discharge port forming member composed of a plastic material, because of their poor compatibility. The insufficient adhesion between the substrate and the discharge port forming member may result in liquid leakage from the flow path or a positional aberration of the discharge port, leading to a drawback that the desired recording may not be achievable.
Secondly, there are required inspection pads for confirming the insulation between the aforementioned anticavitation film and the recording elements or the electrical circuit elements, leading to an increase in the size of the substrate.
In consideration of the foregoing, the object of the present invention is to provide an ink jet recording head and a recording apparatus capable of improving the adhesion between the substrate and the discharge port forming member and minimizing the size of the substrate.
The above-mentioned object can be attained, according to the present invention, by an ink jet recording head in which a discharge port forming member, bearing plural discharge ports for discharging droplets of recording liquid, is formed on a substrate on which plural recording elements for providing the recording liquid with discharging energy and electrical circuit elements for driving the recording elements are formed, the recording head comprising a first metal film covering the upper side of the recording elements and a second metal film covering the upper side of the electrical circuit elements, wherein at least a part of the discharge port forming member is adjoined to the substrate in a portion other than the portion where the first and second metal films are formed, while the discharge ports are so arranged as to form plural arrays, also the recording elements are so arranged as to form an array in the vicinity of each array of the discharge ports, the first metal film is provided over the plural arrays of the recording elements and the first and second metal films are formed as a pair of mutually opposed comb teeth.
The first and second metal films can be anticavitation films composed of tantalum.
The first and second metal films are provided with inspection electrode pads. Another inspection electrode pad is preferably provided in a part of a wiring connected to the electrical circuit elements and the recording elements.
The second metal film may also be grounded.